Project 3 will continue the investigations of variables affecting the development of stimulus control by elements of complex stimuli. The project will contribute to our overall program by developing generally effective procedures for broadening stimulus control in our study population of individuals with severe to moderate developmental disabilities. Proposed Studies 1 and 2 will examine stimulus and reinforcement variables that may affect restricted stimulus control. The experiments will examine (a) whether programmatic methods that are effective with less-complex discriminations can be extended to broaden stimulus control in more-complex discriminations; (b) the effects of intrinsic stimulus salience; (c) the reinforcement variables of predictiveness, correlation, and frequency; and (c) the extent to which stimulus control is exerted by the component attributes vs. configural properties of stimuli; and (d) interactions of stimulus control by components and compounds in stimuli consisting of multiple, discrete elements. Proposed Studies 3-5 will bring together recent technological and methodological advances to obtain extensive and detailed quantification of the individuals's observation of complex stimuli. The experiments will: (a) extend our current methodology to make explicit and record the sequence of externally measurable events that occurs in the observation of single- and multielement stimuli (recording technology appropriate for our study population has recently become available); (b) establish a database describing effective observing in individuals who exhibit accurate discrimination of multiple-element stimuli; (c) determine how effective observing changes as stimulus complexity increases; (d) compare observing in subjects who exhibit broad and restricted stimulus control by multiple-element stimuli; and (e) investigate methods to broaden stimulus control by modifying observing in individuals who exhibit restricted control.